The present invention relates to a method and apparatus for processing thermally developable film. It particularly relates to a compact apparatus and method for developing film by applying radiant heat to the film.
In the conventional practice of color photography, silver halide film is developed by a chemical technique, requiring several steps consisting of latent image development, bleaching, and fixing. While this technique has been developed over many years and results in exceptional images, the technique requires several liquid chemical solutions and precise control of times and temperatures of development. Further, the conventional silver halide chemical development technique is not particularly suitable for utilization with compact developing apparatus. The chemical technique also is not easily performed in the home or small office.
Imaging systems that do not rely on conventional wet processing have received increased attention in recent years. Photothermographic imaging systems have been employed for producing silver images. Typically, these imaging systems have exhibited very low levels of radiation-sensitivity and have been utilized primarily where only low imaging speeds are required. The most common use of photothermographic elements is for copying documents and radiographic images. A method and apparatus for developing a heat developing film is disclosed in U.S. Pat. No. 5,587,767-Islam et al. Summaries of photothermographic imaging systems are published in Research Disclosure, Vol. 170, June 1978, Item 17029, and Vol. 299, March 1989, Item 29963. Thermally developed films have not been generally utilized in color photography. However, heat development color photographic materials have been disclosed, for example, in U.S. Pat. No. 4,021,240-Cerquone et al and U.S. Pat. No. 5,698,365-Taguchi et al, and commercial products such as Color Dry Silver supplied from Minnesota Mining and Manufacturing Co. and PICTROGRAPHY(copyright) and PICTROSTAT(copyright) supplied by Fuji Photo Film Co., Ltd. have been put on the market. Furthermore, U. K. Publication 2,318,645 discloses an imaging element capable of providing a retained viewable image when imagewise exposed and heated. It is proposed that such an element could comprise a color thermal film for photography that delivers satisfactory pictures.
The importance of information such as film type, film speed, film exposure information, and information relevant to the processing and subsequent use (e.g. printing or optical scanning) of the film is well understood. Virtually transparent magnetic layers or stripes on film provide a means to record such information. These magnetic layers or stripes provide for the recording of information during film manufacture, reading and/or recording of information during camera use, and reading and/or recording information during subsequent processing or optical scanning. Film containing a magnetic layer that allows recording of information during manufacture, exposure, and development is disclosed in U.S. Pat. No. 5,215,874-Sakakibara. There is a need to read and write magnetic data on thermographic film associated with the thermal processing. Reading and writing information on a magnetic coating or stripe on thermographic film requires solutions to problems different than those encountered in other apparatus. For example, the thermal development conditions may degrade and potentially erase the magnetic information stored on the film. There is therefore a need to read and store the magnetic information so that it may be rewritten onto the film after thermal processing.
The function of a film scanner is to measure optical density at many points on the film being scanned. The density of each pixel, or smallest region of the film being sensed, is measured by illuminating the region with light of a known light intensity and measuring the intensity of the light, which is transmitted through the film. Color scans require measuring transmitted light intensity over known spectral bands. Such techniques are disclosed in U.S. Pat. No. 5,684,610-Brandestini et al. The transmitted light intensity may be measured electronically and the electronic record of the transmitted light may be digitized and stored as an electronic file representation of the film image.
The importance and utility of an electronic record of film images is widely known in the art. The electronic file may be easily duplicated and extensively manipulated. Color balance and tone scale may be adjusted. Sharpening and other algorithms to alter image structure may be applied. Annotations and/or graphical elements may be added to the film image data file. The scene may be easily cropped and digitally zoomed. An electronic record of a film image may be easily transmitted and communicated through existing electronic communication networks. The electronic record of a film image may also be output to a variety of output devices including ink-jet and thermal wax digital printers. The electronic record may also be manipulated and stored in mass storage devices for rapid retrieval and subsequent processing. There is a need to optically scan thermographic film to provide an electronic file record of the film image information.
Optical writing of sensitometric tables and test patches onto conventional wet processed film to improve imaging system performance is known in the art. Such techniques are disclosed in U.S. Pat. No. 5,667,944-Reem et al. Optical writing of calibrated tablets and patches onto unexposed portions of film is of significant utility. Inspection of processed calibrated tablets or patches allows the processing conditions to be optimized for the remainder of the film strip. Furthermore, analysis of the calibrated tablets or patches allows printing and/or scanning algorithms to be refined to achieve an advantaged print or more useful electronic record of the film image data. For example, tone scale and color balance may be corrected and adjusted based on data obtained from calibrated tablets or patches. Optical writing provides a means to store other information on the film such as data associated with processing or scanning conditions. Optical writing also allows information to be written onto exposed regions of the film. For example, a time and date stamp that is readily apparent in a print may be written onto the film at the time of processing. Furthermore, by controlling the optical writing, graphical elements may be added to the original scene prior to processing. There is a need to provide for optical printing onto thermally developable film.
Thermal processing of photothermographic film may be provided by a conductive, convective, or radiant heating element. Conductive heating elements require physical contact between the heater and the film element, which may lead to undesirable fouling or scratching of the film. Fouling or scratching of the film degrades the ultimate image quality and may result in unacceptable images. Non-conductive heating elements may largely avoid the problems of scratching and fouling by avoiding direct physical contact between the heating element and the film. Non-conductive heating elements include convective and radiant heaters. Convective heaters typically use heated gas to transfer heat to an object. Convective film heaters have been disclosed, for example, in U.S. Pat. No. 4,148,575-Siryj and U.S. Pat. No. 4,198,145-Scott. Radiant heaters provide radiant energy that must be absorbed by an object to heat the object. Radiant heaters are applied in a number of processes. For example, radiant heat system to aid semiconductor wafer processing are disclosed in U.S. Pat. No. 5,444,217-Moore et al and U.S. Pat. No. 4,550,245-Tetsuji et al. Radiant heat systems for drying and curing coatings are disclosed in U.S. Pat. No. 4,771,728-Bergman and U.S. Pat. No. 5,164,571-Asaoko et al. U.S. Pat. No. 5,223,883-Suzuki discloses a radiant heating means to dry photographic film after wet processing. Radiant heating means to develop digital film for xerography has been disclosed in U.S. Pat. No. 5,587,767-Islam et al.
Radiant heating of color photothermographic film is distinct from the radiant heating systems described above and requires new solutions to different problems. Thermal film is light sensitive prior to processing. Exposure to radiant energy comprising wavelengths in which the photothermographic element is sensitive will fog the film and must be avoided to produce acceptable images. Furthermore, conventional film formulations are typically largely transparent in the spectral regions where radiant heaters are expected to operate most efficiently leading to inefficient energy transfer between the radiant heater and the film. Absorbing materials may be incorporated into the photothermographic film to promote efficient energy transfer by producing spectral bands of high absorption. Optimal energy transfer occurs if the spectral bands of high absorption are chosen to coincide with the output spectra of the radiant heater. These bands of high absorption should not interfere with the spectral bands where imaging occurs or image quality will be degraded. Absorbing materials useful to this invention have been disclosed, for example, in U.S. Pat. No. 4,973,572-DeBoer, U.S. Pat. No. 4,948,777-Evans et al, U.S. Pat. No. 4,950,640-Evans et al, and U.S. Pat. No. 4,942,141-Deboer et al.
For the foregoing reasons, there exists a need for a photothermographic film processor that utilizes a radiant heater to avoid scratching or fouling the film by avoiding direct physical contact with the film. In addition there exists a need for a radiant film processor that does not fog the film. There also exists a need for a radiant film processor that promotes efficient energy transfer to the film by emitting radiation in spectral bands where the photothermographic film element strongly absorbs such radiation.
There is a need for a compact thermal film development system with the capability to heat the film without contacting the film. There is a need for a thermal film development system with the capability to provide efficient energy transfer from the radiant heat element to the film. There is a need for a compact radiant thermal film development system that does not fog the thermal film. There is a need for a compact thermal development film system with the capability to scan the thermally developable film. There is a need for a compact thermal development film system with the capability to write optical information onto thermally developable film. There is also a need for a compact thermal development film system with the capability to read and write magnetic information on the film.
It is an object of the invention to overcome disadvantages of prior apparatus and processes for thermal film and the complicated, awkward procedures for wet-processing conventional films.
It is another object to provide heat to the film without physical contact between the heating element and the film.
It is another object to provide efficient energy transfer between the heating element and the film.
It is another object to provide efficient radiant heat to the film without substituted fogging of the film.
It is another object to provide a means to scan the thermal film.
It is another object to provide a means to write optical information on the thermal film.
It is a further object to provide a means to read and write magnetic information associated with the thermal processing on the thermal film.
It is a further object to provide more convenient and rapid processing of thermal film to the individual user.
These and other objects of the invention are accomplished by an apparatus for radiant thermal development of photothermal film comprising a receiving chamber for a film cartridge, drive means to advance thermal film from said film cartridge and rewind film into said film cartridge, an accumulator to gather said film after it has left the cartridge, a source of radiant energy, a guiding means to guide said radiant energy to develop said thermal film as said thermal film passes between said cartridge and said accumulator, a radiant energy absorbing material incorporated into said photothermal film, and a light tight container for said chamber, heater, and accumulator.
The invention provides a compact, convenient apparatus and method for processing of film contained in a film cartridge. It provides a radiant heating apparatus and a method of processing of color photothermal films without physical contact that is efficient, convenient, and compact. It provides a means to scan the thermal film to form an electronic record of image data that may be readily processed, printed, and transmitted. It provides a means to write optical information to alter film image frames and to facilitate optimal thermal processing and scanning by writing sensitometric tables. It also provides a means to record and write magnetic information to effect optimal subsequent processing.